1. Technical Field
The disclosure generally relates to a method of manufacturing a light emitting diode (LED) element, in particular, to a method of manufacturing an LED element with increased yield rate.
2. Description of Related Art
Due to advantages of long lifetime, small volume, high shock absorption, low heat and power saving, LEDs have been widely used in household appliances and indicators or light sources of various instruments. In recent years, LEDs are developing towards rich colorfulness and high luminance, so that the applications of LEDs have been expanded to mega-size display board, traffic light, and so on. It can be expected that LEDs can substitute tungsten lamps and mercury lamps in future and become lighting sources with electricity-saving and environmental friendly functions.
In the related art, LEDs can be fabricated through forming an epitaxy layer on a sapphire substrate. The method is suitable to fabricate LEDs on sapphire substrates by using semiconductor process. The electrodes of the LEDs are conventionally located at the same side of the epitaxy layer. Therefore, the problem of current crowding occurs in the LEDs to limit the heat dissipation efficiency.
To solve the above-mentioned problem, a vertical type LED is provided. To fabricate the vertical type LED, the epitaxy layer is patterned to form a plurality of epitaxy structures separated from each other, and then a passivation layer is formed on the side walls of the patterned epitaxy structures so as to obstruct the leaking current. Afterward, a bonding process is used to bond the epitaxy structures to a carrier substrate, and a laser lift-off process is used to separate the epitaxy structures from the sapphire substrate. Ultimately, electrodes are disposed on the epitaxy structures so as to form a plurality of LED chips.
However, when the laser irradiates the interface between the epitaxy structures and the sapphire substrate, a quite large barometric pressure is produced between the epitaxy structures and the sapphire substrate by the dissipating gases. The gases with high pressure cause peeling of the passivation layer formed on the side walls of the epitaxy structures, which results in poor reliability.